Process of forming catalyst nuclei on substrate, process of electroless-plating substrate, and modified zinc oxide film

Abstract

A substrate includes a non-conductive portion to be electroless-plated of a substrate, on the surface of which fine metal catalyst particles composed of silver nuclei and palladium nuclei each having an average particle size of 1 nm or less adhere at a high nuclei density of 2000 nuclei/mum2 or more. The metal catalyst particles are produced by sensitizing the non-conductive portion of the substrate by dipping the substrate in a sensitizing solution containing bivalent tin ions, activating the non-conductive portion of the substrate by dipping the substrate in a first activator containing silver ions, and activating the non-conductive portion of the substrate by dipping the substrate in a second activator containing palladium ions.

What is claimed is:  
     
       1. A process for forming catalyst nuclei on a substrate, comprising the steps of: 
       preparing a substrate having a non-conductive portion to be electroless-plated;  
       sensitizing said non-conductive portion by dipping said substrate in a sensitizing solution containing bivalent tin ions;  
       activating said non-conductive portion by dipping said substrate in a first activator containing silver ions; and  
       activating said non-conductive portion by dipping said substrate in a second activator containing palladium ions;  
       said sensitizing step and said activating step using said first activator containing silver ions are repeated by several times before said activating step using said second activator containing palladium ions;  
       whereby catalyst particles composed of silver nuclei and palladium nuclei each having an average particle size of 1 nm or less adsorb on said non-conductive portion at a nuclei density of 2000 nuclei/μm 2  or more.  
     
     
       2. The process of forming catalyst nuclei on a substrate according to  claim 1 , wherein said activating step using said first activator containing silver ions and said activating step using said second activator containing palladium ions are repeated by several times before electroless-plating. 
     
     
       3. A process of electroless-plating a substrate comprising: 
       preparing a substrate having a non-conductive portion to be electroless-plated;  
       sensitizing said non-conductive portion by dipping said substrate in a sensitizing solution containing bivalent tin ions;  
       activating said non-conductive portion by dipping said substrate in a first activator containing silver ions;  
       activating said non-conductive portion by dipping said substrate in a second activator containing palladium ions; and  
       electroless-plating said non-conductive portion thus activated by dipping said substrate in an electroless plating solution;  
       said sensitizing step and said activating step using said first activator containing silver ions are repeated by several times before said activating step using said second activator containing palladium ions;  
       wherein catalyst particles composed of silver nuclei and palladium nuclei each having an average particle size of 1 nm or less, at both said activating steps, adsorb on said non-conductive portion at a nuclei density of 2000 nuclei/μm 2  or more.  
     
     
       4. A process of electroless-plating a substrate according to  claim 3 , wherein said electroless plating solution is selected from the group consisting of an electroless nickel plating solution, an electroless copper plating solution, and an electroless zinc oxide plating solution. 
     
     
       5. A process of electroless-plating a substrate according to  claim 3 , wherein said substrate is a silicon substrate on the surface of which either of a Ta film, a TaN film and a TiN film is formed, and said electroless plating solution is the electroless copper plating solution. 
     
     
       6. A process of electroless-plating a substrate according to  claim 3 , wherein said substrate is a printed wiring board having a through-hole, a peripheral wall portion of which is taken as said non-conductive portion to be electroless-plated, and said electroless plating solution is the electroless copper plating solution. 
     
     
       7. A process of electroless-plating a substrate according to  claim 3 , wherein said substrate is a polycrystalline glass substrate, and said electroless plating solution is the electroless nickel plating solution. 
     
     
       8. A process of electroless-plating a substrate according to  claim 3 , wherein said substrate is a transparent substrate, and said electroless plating solution is the electroless zinc oxide plating solution. 
     
     
       9. The process of electroless-plating a substrate according to  claim 3 , wherein said activating step using said first activator containing silver ions and said activating step using said second activator containing palladium ions are repeated by several times before said electroless-plating step. 
     
     
       10. A process of producing a modified zinc oxide film, comprising the steps of: 
       preparing a transparent substrate having a non-conductive portion to be electroless-plated;  
       sensitizing said non-conductive portion by dipping said substrate in a sensitizing solution containing bivalent tin ions;  
       activating said non-conductive portion by dipping said substrate in a first activator containing silver ions;  
       activating said non-conductive portion by dipping said substrate in a second activator containing palladium ions;  
       electroless-plating said non-conductive portion thus activated by dipping said substrate in an electroless zinc oxide plating solution, to form a zinc oxide film;  
       treating said zinc oxide film with a modifier composed of a water solution containing trivalent cations; and  
       heating said zinc oxide film thus treated;  
       wherein catalyst particles composed of silver nuclei and palladium nuclei each having an average particle size of 1 nm or less, at both said activating steps, adsorb on said non-conductive portion at a nuclei density of 2000 nuclei/μm 2  or more.  
     
     
       11. A process of producing a modified zinc oxide film according to  claim 10 , wherein said heating step is performed at a heating temperature ranging from 150° C. to 700° C. 
     
     
       12. A process of producing a modified zinc oxide film according to  claim 10 , wherein said heating step is performed in a heating atmosphere selected from air, a non-oxidizing gas atmosphere, and a mixed gas atmosphere thereof.